A judge in Chile has ordered that the body of poet Pablo Neruda should be returned to his grave for reburial alongside the remains of his third wife, Matilde Urrutia, putting an end to an international investigation into the cause of his death in 1973.

For nearly two years, Neruda’s remains have been lying in forensic laboratories in three countries – and from early this year in a fourth – in an attempt to determine whether his death may have been accelerated by poisoning.

Neruda, who won the Nobel prize for literature in 1971, was being treated for cancer. He had been intending to present eight new books to the world to mark his 70th birthday in 1974, but he died on 23 September 1973, 12 days after Augusto Pinochet’s military coup. All eight books were published posthumously.

In 2011, the poet’s former driver, Manuel Araya, told the Mexican magazine Proceso that Neruda, a longtime member of Chile’s Communist party, had been murdered by an injection to his stomach by political enemies as he lay in his hospital bed in the Chilean capital, Santiago. In 2013, a judge ordered the exhumation of Neruda’s body to investigate Araya’s claims.

His bones were examined by forensic scientists in Santiago, North Carolina in the US and Murcia, Spain. In November 2013, forensic experts announced that they had found no evidence of poisoning, although the investigation was not formally ended.

On 21 January 2015, the Chilean government announced that it was reopening the case. New tests were ordered which, instead of looking for traces of poison, have been examining whether inorganic or heavy metals could have indirectly caused the poet’s death. Further tests were also initiated at a laboratory in Switzerland.

Now Mario Carroza, the Chilean judge in charge of the case, has issued new instructions for Neruda’s body to be returned in April to his grave in front of his beloved coastal home at Isla Negra. One of Neruda’s nephews, Rodolfo Reyes, denounced the decision.

Reyes, a lawyer, said it was important to exhaust all possible tests on the poet’s body before he is reburied. Reyes remains convinced that the poisoning allegations deserve serious attention.

Supporters of this theory point out that on 22 September 1973, the day before his death, Neruda had been offered safe passage out of Chile to Mexico, from where he would have represented a serious political threat to the military junta in Santiago. The poet chose to delay his departure.

It has also been pointed out that another political opponent of the regime, former president Eduardo Frei Montalva, died in the same Santiago hospital, the Santa María Clinic, in 1982 after expressing his opposition to the military dictatorship. Frei’s death was initially attributed to septic shock during a routine operation, but a 2006 investigation proved that he had been assassinated with mustard gas and thallium.

Another of Neruda’s nephews, Bernardo Reyes, is delighted that the poet’s remains are returning to his homeland. In a strongly worded statement, Bernardo Reyes declared: “The time of the loudmouths, mythomaniacs and upstarts is finally coming to an end. Those who crudely made use of a supposed witness to an imaginary murder will have to face the consequences.”

More than four decades after his death, Neruda’s poetry remains as powerful as ever. From early this year, trains on Santiago’s Metro have been emblazoned with text from his celebrated 1924 collection, Twenty Love Poems and a Song of Despair. A debate is still raging in Chile over whether to rename Santiago Airport after the poet.

Adam Feinstein’s biography, Pablo Neruda: A Passion for Life, was re-issued by Bloomsbury in 2013